1. Field of the Invention
The present invention relates to an electric tool, including a hammer mechanism, a drive motor for driving the hammer mechanism, a gear for connecting the drive motor with the hammer mechanism, a ventilator wheel connected with an exhaust opening, and separate air channels having each a section opening, with one of the air channels being associated at least with the gear, and another of the air channels being associated at least with the drive motor.
2. Description of the Prior Art
Because of high temperatures, which are generated in an electric tool, in particular in a drilling and chiseling tool, the electric tool is provided with a cooling device which permits to increase the service life of the drive motor and the gear which connects the drive motor with the hammer mechanism.
In a majority of electric tools, a ventilator, which serves as a cooling device, is provided on the commutator side of a rotor of the drive motor. The ventilator provides for suctioning of a cold environmental air through a suction opening formed in the tool housing, and for flow of the air past the gear and through the drive motor. The cold environmental air cools first the gear, then the drive motor and is discharged through an exhaust opening formed in the housing cover.
A drawback of this cooling device consists in that the cooling air is heated as it passes past the gear and is not capable of adequately cooling the drive motor. A further drawback of this cooling device consists in that that a large portion of the boring dust and dust particles, in particular during an overhead work, is aspirated into the drive motor through the suction opening. This significantly reduces the service life of the drive motor because the dust and drillings cause erosion of both the rotor and the stator of the drive motor.
To eliminate this drawback, German publication DE-196 00 339 proposes an electric tool in which the gear and the drive motor are cooled with the cold environmental air separately and independent from each other. The cold environmental air is aspirated by a ventilator through two suction openings, with the cooling air flowing through two separate air channels over both the gear and the drive motor and with the air being discharged through two exhaust openings. The ventilator is mounted on the drive motor shaft and is located between the drive motor and the gear. One of the channels extends through the gear to one side of the ventilator, and the other of the channels extends through the drive motor to another side of the ventilator. The ventilator is provided, on each of its sides, with a separate blade which is associated with a respective channel.
A serious drawback of the tool disclosed in DE-19 000 339 consists in that the ventilator wheel is arranged between the drive motor and the gear. This results in a time-consuming operation associated with mounting of the wheel and its eventual necessary replacement. A further drawback consists in the high costs of the wheel itself which is made of two parts.
Accordingly an object of the present invention is to provide an electric tool which would be simple to produce and to assembly and which, at the same time, would insure a required cooling of the gear, the drive motor, and other elements of the tool.